Device in a shaft furnace



INVENTOR WM 5 y 1 j g Filed March 29, 1956 J E- WIKLUND DEVICE IN ASHAFT FURNACE Feb. 23, 1960 ATTORNEYS 2,926,009 DEVICE IN A SHAFTFURNACE: Johan Elof Wiklund; Halsingborg, Sweden Application March 29,1956, Serial No. 574,899

Claims priority, application Sweden April 13, 1955 3 Claims. (Cl.263-29) This invention relates to a shaft furnace and particular- 1y tomeans for the introduction of gas, preferably a hot gas, into the shaftand withdrawal of the same therefrom.

The problem of blowing in or withdrawing hot gas through the wall of ashaft furnace arises e.g. in connection with pelletizing recuperativefurnaces, i.e. wherein the material is chilled by means of air, whichthen is introduced into a combustion chamber to act as combustion airfor injected oil, and the hot combustion gases thus produced areintroduced into the shaft through inlet orifices in the wall of theshaft.

In order to prevent clogging of said inlets attempts have been made togive the inlets several difierent shapes. It has been tried, forinstance, to considerably increase the cross sectional area of the shaftin the zone where the hot gas is introduced, the idea thereof being thatthe material moving downwardly might form a free cave surface at thelevel of the widening of the shaft, and that said inlets when placedadjacent said free cave surface might be maintained free from material.It has been found, however, that the material tends to jam where theshaft widens. One circumstance that contributes to this is that no upperpressure will be exerted on the material that forms the free cavesurface, for which reason said material tends to adhere to the wall ofthe furnace. Once such adherence has occurred the amount of adheredmaterial continuously increases so that the flow in the furnace ceases.

It also has been suggested to form the hot gas inlets as perforatedblocks, constituting a part of the furnace wall. It has been found,however, that the material enters into the perforations far too easilyand chokes up said perforations.

According to the present invention these drawbacks are avoided, so thatthe gas may be fed into the shaft furnace without danger of clogging andjamming in the furnace. The furnace according to the invention comprisesducts, extending through the wall of the furnace, and is characterisedin that the cross sectional area of the ducts increases from theinternal surface of the furnace wall to the external surface of saidwall, and that the lowermost surface of the ducts is inclined so as toform an acute angle with the internal furnace Wall surface.

Inasmuch as the ducts are formed with an outwardly directed draft, i.e.their cross sectional area increases outwardly from the internal wallsurface, pieces of material that inadvertently enter the ducts mayeasily pass and do not jam up in the ducts.

Inasmuch as the lowermost surfaces of the ducts are inclined downwardlythese surfaces do not provide any hold for the material wherefore piecesthereof that have entered into a duct slide outwardly along saidinclined surfaces.

Theoretically the ducts may be formed with any cross sectional areadesired, provided that the above mentioned requirements are compliedwith. However, it

- United tates Patent M 2,926,009 Patented Feb. 23, 1960 ICC has beenfound particularly advantageous to form the ducts as verticallyextending slots. Therefore, the invention will hereinafter be describedmore in detail with reference made to a sintering furnace with gasinlets and outlets having the formof such vertically extending slots.

In the drawing Fig. 1 shows a shaft furnace with its combustion chamberin a vertical section and Fig. 2 is a section along line IIII of Fig. 1.

The assembly comprises a shaft furnace 1, having a combustion chamber 2.The wall 3 between the furnace and the combustion chamber is built up astwo upright vaults, having the shape of arcs with centres at the points7 and 8 respectively in the opposite combustion chamber Wall 9. In thevaults there are arranged one above the other two rows of wedge-shapedbricks, positioned so as to form between themselves vertically extendingslots or ducts 5 and 6 respectively. The bricks are shaped so that thelowermost surfaces of the slots are inclined at an acute angle withrespect to the internal furnace surface. Each of the slots 5, 6 betweenthe bricks 4 has a horizontal cross section that widens from the shafttowards the combustion chamber.

Inasmuch as the Wall 3 has an arcuate shape and the bricks extendradially therein the slots 5 will be readily accessible for cleaningfrom the center of the arc, i.e. the points 7 and 8 respectively. Atthese points there are arranged openings 11 and 13 respectively, havingthe dual purpose of serving as cleaning and inspection openmgs.

Openings 15 for oil burner nozzles are arranged in the combustionchamber walls. In the bottoms of the combustion chambers there arearranged outlet openings 17 for material that enters through the slots 5and falls down into the combustion chambers. openings 17 the materialthen by means of devices that are not shown is passed away to join thematerial which is fed from the bottom of the furnace. The amount ofmaterial entering into the combustion chambers is very low. This is duepartly to the inherent tendency of the material to form bridges andpartly to that the material is partially melt and thus less mobile.

The operation of the sintering furnace is as follows: The material to besintered, e.g. ore slick balls is loaded in at the top portion of thefurnace. Air is blown in at the bottom portion of the furnace and flowsupwardly to meet the hot sintered material, which then will be chilled.The air, having thus been pro-heated, flows on the one hand straightupwardly through the shaft and on the other hand into the combustionchamber 2 through the slots 5. Oil is injected into the combustionchamber and will burn with the pre-heated air acting as combustion air.The hot combustion gases leave the combustion chamber through the upperslots 6. The proportion of the air blown in at the bottom of the furnacewhich passes through the combustion chamber will be determined by therelation between the flow resistances of the combustion chamber and thematerial column of corresponding height respectively.

In order to permit distribution of the hot combustion gas over theentire cross sectional area of the shaft the height of the verticalslots should at least correspond to half the width of the shaft.

I claim:

1. In a shaft furnace having a vertical shaft adapted to receive adownwardly directed load of material to be treated and an upwardlydirected passage of air, a combustion chamber secured externally to onewall of said shaft and extending laterally outwardly therefrom, andhaving a wall opposite the said one wall of the shaft, said wall of saidcombustion chamber opposite said shaft From the outlet 3 wall havingvertically spaced openings therein, a portion of said shaft wall havingan arcuate configuration in horizontal cross section, the center of theare being located on a vertical line extending centrally through saidcombustion chamber opposite wall openings, said shaft wall arcuateportion having a plurality of lower ducts therein opposite one of saidcombustion chamber opposite wall openings for admitting the upwardlydirected air from the vertical shaft into the combustion chamber andalso a plurality of upper ducts therein oppositeione of said combustionchamber opposite wall openings for introducing the heated gases of thecombustion chamber substantially vertically into the vertical shaft, thevertical cross sectional area of each of said ducts increasing outwardlyfrom the internal shaft surface of the furnace wall toward thecombustion chamber and the lower surface of each of said ducts beingdownwardly inclined and forming an acute angle with the internal furnacewall surface, whereby said ducts may be readily cleaned from theopenings in the opposite wall of the combustion 4 chamber located at thecenter of the arc of the furnace shaft arcuate portions.

2. A shaft furnace as defined in claim 1 wherein the bottom of saidcombustion chamber has an outlet opening therein for discharging solidmaterial entering into' said combustion chamber through said ducts.

3. A shaft furnace as defined in claim 1 wherein each of the ducts has aheight at least as great as half the distance between the wallintermediate the combustion chamber and the vertical shaft and theopposite wall of said vertical shaft.

References Cited in the file of this patent UNITED STATES PATENTS

